1. Field of the Invention
The present invention relates to an electric contact apparatus for inspecting a liquid crystal display panel, more specifically relates to an electric contact apparatus for supplying driving signals for inspecting a liquid crystal display panel into electrodes arranged on an insulating substrate of the liquid crystal display panel.
2. Description of Related Art
In general, a conventional liquid crystal display apparatus comprises a liquid crystal display panel and a plurality of flexible printed circuit boards. The liquid crystal display panel comprises an insulating substrate made of glass, a display portion formed on the insulating substrate and including therein a plurality of display elements, and a plurality of electrodes arranged on the insulating substrate and connected respectively to the display elements. On the other hand, each of the flexible printed circuit boards comprises a flexible insulating sheet, a plurality of conductive terminals arranged on the insulating sheet, and an integrated circuit (IC) device mounted on the insulating sheet and connected to the conductive terminals. Driving signals for driving the liquid crystal display panel are generated from the IC device and then supplied into the display elements of the liquid crystal display panel through the conductive terminals and the electrodes. Generally, the liquid crystal display apparatus has been fabricated by securing the flexible printed circuit boards to the insulating substrate of the liquid crystal display panel by heat sealing or the like for electrically connecting the conductive terminals to the electrodes of the liquid crystal display panel.
Conventionally, the display operation of this type of liquid crystal display apparatus has been inspected by supplying certain driving signals generated from the IC devices into the display elements of the liquid crystal display panel and inspecting the state of operation or the quality of display of the display portion of the liquid crystal display panel at that time by the naked eye. In the case of such a liquid crystal display apparatus, the display elements in the display portion of the liquid crystal display panel can be easily driven by connecting the flexible printed circuit boards heat-sealed on the insulating substrate to an external driving apparatus through connectors. However, where a defect is found during the inspection of the liquid crystal display apparatus, even in a case where the cause of that defect resides only in the liquid crystal display panel, the flexible printed circuit boards and IC devices mounted on the flexible printed circuit boards have to be treated as defective parts together with the liquid crystal display panel, resulting in the increase of manufacturing cost. Accordingly, it is desirable to inspect the state of operation or the quality of display of the liquid crystal display panel before the flexible printed circuit boards are fixed to the insulating substrate of the liquid crystal display panel.
For this purpose, an electric contact apparatus having a plurality of contact elements for establishing direct contact with the electrodes on the insulating substrate of the liquid crystal display panel and for supplying driving signals for inspection onto the electrodes has been proposed. A conventional electric contact apparatus has a plurality of needle-like probes or a plurality of loop-like wire probes spring-biased in the direction of projection as the contact elements.
In recent years, along with the increasing density of display elements in liquid crystal display panels, the electrodes arranged on the insulating substrate of the liquid crystal display panels and the pitches between the electrodes have been made increasingly narrower and the number of the electrodes has become extremely large. However, there is a limit in the dimensions and machining precision to how far the needle-like probes or the loop-like wire probes can be miniaturized and provided in an insulating support to match with the pitch of the electrodes of the liquid crystal display panel. Also, miniaturized needle-like probes or loop-like wire probes become very weak and therefore become insufficient in durability and, at the same time, their handling becomes very difficult. The risk of poor conduction or short-circuits due to deformation of these probes is increased. Further, an expensive precision machining technique is necessary for the fabrication and assembly of these fine probes and the connection of the lead wires to the probes. Therefore, an electric contact apparatus provided with the same number of probes as the number of the electrodes of the liquid crystal display panel becomes very expensive.
Note that, if the display operation of the liquid crystal display panel is inspected in units of driving modules, the number of the probes of the electric contact apparatus can be reduced, but it is necessary to repeat the inspection for every driving module, and therefore much labor and time are required, and the inspection efficiency is considerably lowered. Also, the entire display portion of the liquid crystal display panel cannot be simultaneously made to operate by the method of repeating the inspection for every driving module, so it becomes difficult to identify the existence of defects such as uneven color, uneven luminance, etc. in the entire display portion of the liquid crystal display panel.